my check engine light just came on after some tinkering in my engine bay. all i did was remove the exhaust manifold heat shield, and to do that i had to disconnect a wiring harness to some wires that went in thru a hole in the shield. im not sure what they are for but apparently my engine didnt like it. im not sure what else could have caused the light to come on because the only other thing i did was replace the drivers side fender.

any ideas?

 

The harness you disconnected was most likely leading to your o2 sensor. Check to see if you connected it properly.

Also, find out what this code is. It'll help us all understand what your problem might be.

How to check CEL

 

You probably disconnected your o2 sensor. Make sure they're plugged in tightly and not damaged in any way. After you plug everything back in securely, disconnect your negative battery cable for 5 minutes, then start your car. The light should go out.

 

it was in fact the wiring harness form the O2 sensor. i disconnected the neg battery cable and the light still came on a few seconds after starting up the engine. i havent put the heat shield back on yet, so could that have anything to do with it?

edit:
i ran the self diagnostic test for the CEL and found it was the oxygen sensor heater (trouble code 41). everything is connected properly, the heat shield was replaced, and i disconnected the neg terminal of the battery for over 5 mins, but the CEL is still coming on. any help?

 

bump to the top

 

Could you possibly have damaged the harness, or did the heat shield ever come in contact with the altertator? If you touched the alternator with the heat shield, then it could have blown out your sensor. There would have been sparks if that happened and you'd know it.

Inspect the harness and plug to make sure everything's kosher. It's a little weird for the heater circuit to go bad after removing a heat shield. Were there any ground straps on the heat shield?

 

there were no sparks, and i dont think there was any way i could have damaged the harness. everything looks the same as it did before i pulled the heat shield off. im stumped. there isnt any change in performance, but its unnerving driving with the CEL on

 

bump

 

There most likely IS some change in performance - your ECU is now in limp mode, it will operate only from pre-programmed air/fuel maps. Sounds like your O2 sensor just died.